1. Fields of the Invention
The present invention relates to a portable illumination device for modifying circadian rhythms, and more particularly to such a device which is worn by a subject to direct the light for stimulating the eyes of the subject to the person's eyes to modify biological rhythms and enhance wakefulness.
2. Description of the Prior Art
A bright lighting therapy has been known for treatment of disorders of biological rhythm, i.e. an internal biological clock as well as of sleep and wakefulness cycles. The bright lighting therapy is found effective to treat morbid disorders such as seasonal affective disorders (SAD), endogenous depressions, sleep/wake rhythm disorders, and biological disorders accompanying abnormal behaviors frequently seen in mentally handicapped persons, as well as non-morbid disorders such as jet lag and tiredness associated with shift work.
The bright lighting therapy utilizes a high intensity artificial light source to stimulate the eyes of a subject at a suitable timing for a selected time period in accordance with symptoms of the subject. Due to the requirement of the high intensity light, a device realizing the therapy is normally expected to be bulky and is not suitable for treatment of unserious disorders without disturbing daily activities of the subject. To this end, WO/89/08475, WO/89/08476, and WO/94/09851 propose a portable light illumination device for stimulating neuroendocrine system which is designed to be carried on a subject's body and delivers a high intensity light to eyes of the subject, while permitting the subject to proceed with daily activities during the treatment. However, since this portable device relies on a point or line source of light to produce the high intensity light and the light source is mounted on the bill of a visor to deliver the light directly or indirectly to the subject's eyes, the high intensity light source itself or virtual image thereof will remains in the field of view of the subject to greatly dazzle the subject. With this result, the subject has to narrow one's eye to receive only a reduced amount of light and therefore eventually fail to have effective treatment.